Machines for producing high pressure, small diameter fluid jets containing abrasive materials are used to cut materials such as metals, ceramics and concrete. For some lower strength materials, such as soft foam or food, the fluid jet alone is sufficient to do the cutting. The machines are commonly referred to in the art as water jet or fluid jet cutting machines and typically feature cutting heads that are connected to high pressure water pumping systems to establish an ultra-high pressure water jet. The standard in the industry is to have a cutting head that is moved relative to a workpiece to produce the desired cuts in the workpiece. The fluid jet, following passage past the workpiece, and the particulate material of the cut workpiece are collected below the workpiece for appropriate disposal. Often a large tank is placed below the workpiece to achieve the collection of the liquid and particulates or, in some machines, a smaller collector that moves with the above positioned nozzle head is relied upon.
FIG. 1 shows an example of a typical prior art waterjet cutting machine which uses the benefit of added abrasive for increased cutting ability. In FIG. 1 there is shown abrasive liquid jet cutting system 10 which uses water and abrasive for cutting. Workpiece 11 is a stationary plate typically of rigid and/or semi-rigid material, such as plastic, metal, ceramic, concrete, composite materials and the like. Work table 12 is a generally rectangular frame that supports workpiece 11 such that the workpiece stays in position as the cutting head carries out a preprogrammed pattern. Table 12 has a hole in it which is under the workpiece and is dimensioned to correspond with the particular product being formed or can be replaced with a disposable grating for a greater latitude of possible product size formation.
The prior art abrasive liquid jet system 10 in FIG. 1 has an intensifier, indicated generally at 13, operable to provide a continuous supply of water under ultra high pressure to a cutting head indicated generally at 14. Ultra high pressure water is under pressure of at least 30,000 psi. The water pressure developed by intensifier 13 is typically in the range of 30,000 to over 100,000 psi. Cutting head 14 accommodates a supply of grit or abrasive materials introduced to cutting head 14 through side tube 16. A continuous supply of grit is directed into tube 16 from a grit source such as hopper 38 and associated supply tube 39. The grit is entrained within the high velocity jet 17 of water that is discharged through an elongated tubular nozzle 36 at the lower end of cutting head 14. Nozzle 36 projects downward toward the top of workpiece 11.
An X-Y drive control assembly 18 which is programmed by a computer (not shown) controls the movement of cutting head 14 relative to workpiece 11 to provide a selected cut in workpiece 11 to make a product.
As also shown in FIG. 1, the high velocity liquid jet 17 containing the abrasive material cuts through workpiece 11. The water, abrasive material and particulate materials of workpiece 11 are then directed downwardly into a catcher or receiver indicated generally at 19. Receiver 19 collects the water, grit and particulate materials of workpiece 11 and discharges these materials into a settling tank or some other means of disposal.
Intensifier 13 has a piston and cylinder assembly, forming hydraulic motor 21, that sequentially operates piston pumps 22 and 23 to elevate the pressure of the water to the ultra high pressure range. Hydraulic motor 21 is operated in response to hydraulic fluid under pressure derived from a pump 26 driven by a motor 27. The hydraulic fluid is withdrawn by operation of pump 26 from a reservoir 28 and discharged into a solenoid operated reversing valve 30 operable to selectively supply hydraulic fluid under pressure to opposite ends of hydraulic motor 21 and return fluid back to reservoir 28. The ultra high pressure water flows from pumps 22 and 23 through check valves 29 and 31 into attenuator 32 which provides for a constant flow rate of water to cutting head 14. The ultra high pressure water is delivered to a linear chamber 34 of a generally upright body 33 of cutting head 14. The water flows through a small opening in a sapphire, ruby, diamond or corundum element (not shown in FIG. 1) located adjacent the upper end of nozzle 36. Grit is introduced into the stream of water flowing between the sapphire element and the upper end of nozzle 36. A mixture of grit and water flows through nozzle 36 and is discharged therefrom as a high velocity small diameter waterjet 17.
FIG. 2 also shows a conventional, prior art waterjet cutting machine which has features similar to those schematically shown in FIG. 1. FIG. 2 shows in greater detail the movement means 40 provided for the X-Y movement of head assembly 42 (with cutting nozzle). Movement means 40 provides both support and movement in head assembly 42 as it features gantry crane system 43 with adjustable X-axis beams 44, 46 supported at their ends by corner support structures 48, 50, 52 and 54 and crossbeams 56, 58. This overhanging arrangement, in combination with the suspended head assembly, leads to a degree of inertial head assembly shaking if the head assembly is accelerated or decelerated too fast or if there is a rapid shift in direction. This shaking leads to inaccuracies in cutting and requires the operator to ramp up or down the speed during initial start up and stopping and to avoid rapid turns.
Positioned below head assembly 42 is tank frame 60 which provides strength to catch tank 62 having a sloped bottom. A drag chain (not shown) or the like is used to periodically purge the large tank of grit and product water. Frame 60 provides support to a large grate 61 of relatively inexpensive material which is cut together with the workpiece and periodically replaced.
FIG. 2 further shows control stand 64 which provides for programming or the like and which communicates with controller 65 supported on support 52 through which all the moving components in the system can be controlled. This includes the peripherally positioned intensifier 66 which is connected via high pressure piping system 67 to intermediate water reception area 68 with gauge and filter assembly and from which extends high pressure water tube assembly 70 with its in-line swivel elbows to accommodate for nozzle head shifting. Tube 70 is connected to head assembly 42.
Additional peripheral members include hopper 72, which is connected, via tube 74 (partially shown), to head assembly 42, and settlement tank 76 (the latter shown unconnected but would be in communication with tank 62). Hopper 72 is pressurized (e.g. a diaphragm arrangement) to force abrasive out of the hopper and to the nozzle head. Although not shown, additional peripheral items available in the prior art include chillers (for the hydraulic pump) and reverse osmosis water purifiers positioned upstream of the intensifier.
The prior art system illustrated in FIG. 2, with its X-Y plane adjustable head assembly occupies a relatively large space (e.g., length L1 of approx. 100" along X-axis, a Y-axis length L2 width of 60" length and a Z-axis height L3 of about 93"). Moreover, the large tank required to cover the possible X-Y movement of head assembly 42 occupies a large percentage (e.g., 80%) of the X-Y axis area (L1.times.L2) and peripheral components (some of which are not shown) are spaced outside of the tank's periphery so as to increase floor space usage, still further. For example, rather than repeatedly having to shut down the system to clean out catch tank 62 conventional systems often employ an automated scraper or drag chain assembly for abrasive removal. The scraper chain assembly takes up another three feet or so further out from catch tank 62. Because of this large floor space usage many job shops or the like are unable to utilize such prior art fluid jet systems because of the unavailability of that much space and/or the cost for such space usage.
Due to the multitude of peripheral components associated with the conventional systems, each component requires an individual containment enclosure or is left open. For example, the larger conventional systems such as that shown in FIG. 2 feature an open gantry frame arrangement with this openness resulting in a large deal of waste and debris being splattered or strewn about the system, making for a messy work environment.
Also, the high pressure piping line, which includes piping system 67 originating at intensifier 66 and tube assembly 70 which, ends at the nozzle head assembly 42, and which also includes intermediately positioned filter 68 and swivel elbows, etc., typically runs about 50 feet or so. This length of tubing and the myriad of changes in flow direction leads to losses in energy which otherwise could be used to enhance the speed and capability of the cutting fluid jet.
Additional problems associated with such prior art systems include the relatively high cost for an entire system, lack of flexibility for handling different shaped objects to be cut, difficulty in switching over from one cutting abrasive to the next or resupplying an emptied container, cutting accuracy difficulties (especially with temperature expansion and contraction of the gantry frame), loads on floor space, difficulties in maintenance and repairs, tooling inflexibility etc.